Willkommen! If it were mine I'd clean it up really good and head to the range to see how it shoots. If it functions properly and shoots straight then I wouldn't worry about it. Yes, the barrels that Bushmaster went with on the ACR are heavier profile than I think they needed to be. My take was they did not want to build or source specific barrels and so just went with the AR-15 / M-4 profile barrels they already had. The bad news is the weight, but the good news is that both of mine have been quite accurate.
Hope it works out and you can keep it. Enjoy!